This invention relates to medical devices and particularly to powering medical devices with electrical energy converted from mechanical energy.
Conventional electrical medical devices receive their electrical energy from either a direct power line or from a battery. Such medical devices include cardiac defibrillators, electrocardiographs (stationary recorders and ambulatory xe2x80x9cHolterxe2x80x9d or event recorders), transport monitoring equipment and other electrical medical devices.
One such medical device is a cardiac defibrillator, which discharges electrical energy into a patient to restore a normal rhythmic heartbeat. The normal rhythmic heartbeat can be disrupted for several reasons. For example, cardiac arrest occurs when there is a sudden cessation of a heartbeat, or when there is a loss of effective pumping of blood by the heart. Typically, cardiac arrest is caused by arrhythmias, which abruptly cease circulation throughout the body and vital organs. Without rapid resuscitation, victims of cardiac arrest become permanently injured or die. Typically, arrhythmias are caused by disturbances in the electrical conduction mechanism of the heart. One type of arrhythmia, fibrillation, occurs where the electrical activity causes the heart to twitch rapidly, replacing the normal rhythmic heartbeat. Defibrillation is the process of restoring the heart to its normal rhythmic heartbeat. Typically, defibrillation occurs when a defibrillator operator, such as a physician, paramedic or other emergency care personnel, administers one or more electric charges or shocks to the patient using a defibrillator. Defibrillators are either implantable, meaning the device operates in vivo, or external, meaning the device acts from outside the body.
Cardiac defibrillators include circuitry, a capacitor, and a power source. The power source for conventional defibrillators is either an AC power source (e.g., from an electric power line) or a battery. The circuitry of the conventional defibrillator passes electrical energy from the power source to the capacitor. Then when the defibrillator operator instructs the defibrillator to deliver the shock, the stored charge of the capacitor is discharged into a patient to provide a therapeutic shock.
FIG. 1 shows the general arrangement of a conventional defibrillator 10. Conventional defibrillator 10 includes a battery 20, a control unit 30, a charging circuit 40, a capacitor 50, a patient interface 60, and a printer 70.
Battery 20 supplies electrical energy to control unit 30 and to capacitor 50 through charging circuit 40. If battery 20 is rechargeable, defibrillator 10 typically also includes an external battery charger 25.
Control unit 30 controls the operation of defibrillator 10. When the defibrillator operator instructs defibrillator 10 to deliver the charge to the patient, control unit 30 signals capacitor 50 to pass the stored charge to the patient through patient interface 60. Control unit 30 may also include a display (not shown) for the defibrillator operator to view (such as a conventionally known backlit LCD or the like).
Charging circuit 40 transfers the electrical energy from battery 20 to capacitor 50. Generally, charging circuits include a power conditioning circuit (not shown), which receives power from battery 20, and a transformer or rectifier circuit (not shown) coupled to the conditioning circuit and intermediate the power conditioning circuit and capacitor 50. Charging circuit 40 increases the voltage supplied from the battery 20 and outputs the increased voltage to the capacitor 50. Capacitor 50 holds the charge until it is delivered or discharged into a patient through patient interface 60.
Capacitor 50 and control unit 30 are electrically coupled to patient interface 60. Patient interface 60 usually includes either pads or paddles (not shown) that are placed in physical contact with the patient by the defibrillator operator. The paddles may range in size according to the expected use (e.g., pediatric to adult patients) and preferably include charge/shock and printer buttons. For example, the paddles may range in size from approximately 17 cm2 (or smaller) to approximately 80 cm2 in area (or larger). The pads include an adapter cable for adult and pediatric pads. When pads are used, the buttons for charge/shock and printer are located elsewhere on the defibrillator (e.g., on control unit 30).
Printer 70 is electrically coupled to control unit 30, and is used to output rhythm strips and textual information before, during, and after operation.
Generally, conventional defibrillators receive their electric energy from either an AC source (such as a power line) or a battery (e.g., disposable or rechargeable). When power line electricity is used, the use of the defibrillator is limited to situations where line power is available and reliable. Line power is not available or reliable when, for example, there are blackouts, brown outs, natural disasters, or the like. Battery powered defibrillators are mobile but limited in other ways and thus have several disadvantages. For example, after a defibrillator has been used, or after a set maintenance interval, the battery must either be replaced or recharged by the external battery charger. After numerous recharges by the battery charger, a rechargeable battery should be replaced as its effective charge retention diminishes. Also, a battery adds significant size and weight to a battery-operated device""s overall configuration. In addition, batteries have a limited power supply, which requires defibrillator operators to charge and monitor battery energy levels. When the defibrillator is a mobile unit, battery charging or battery replacement may not be an option, due to a lack of a power source for recharging, or for a lack of spare batteries. Further, while a defibrillator sits for an extended period of time, the batteries gradually lose their energy supply, or degrade.
Thus, there is a long felt need for a medical device (such as a cardiac defibrillator) that is mobile and does not rely on a battery or line power as a power source. A medical device that receives its energy from a source of mechanical energy would be advantageous in various applications. For example, conventional medical devices that are operated by hospital personnel (xe2x80x9cin-hospitalxe2x80x9d) or by trained personnel before the patient can be brought to the hospital, e.g., by paramedics (xe2x80x9cpre-hospitalxe2x80x9d) require a reliable power source. Maintenance errors, or malfunctioning or degraded power sources, may all adversely affect the power source reliability. For pre-hospital and in-hospital uses, errors that occur during monitoring and maintenance of battery charges or line power failures could be eliminated by a medical device having an alternative power source.
Also, an electrical medical device that operates without batteries or line power is advantageous for an emerging application for certain medical devices (such as defibrillators): xe2x80x9cfire extinguisherxe2x80x9d medical devices. Fire extinguisher defibrillators are located in places (e.g., wherever fire extinguishers are located) where they will be needed to provide easy and reliable operation, even by untrained personnel. Such defibrillators would be better served if there were no batteries to degrade over time or line power to fail. These defibrillators would thus not be affected by the battery or line power problems associated with smoke detectors.
Further, battery powered medical devices have disadvantages in foreign applications. For example, certain batteries may not be available in certain countries. Also, because of environmental laws, use and disposal of certain batteries is difficult. Further, battery rechargers and line power medical devices must be designed or adapted to use with the foreign power source.
Likewise, other mobile electrical medical devices would benefit from having a mechanical energy power source.
Accordingly, it would be advantageous to provide an alternate method of energizing medical devices. It would also be advantageous to provide a source of recharging the discharge capacitor of certain medical devices that eliminates the need for batteries and external battery charging. It would be further advantageous to not charge medical device""s circuitry from stored electric power in a battery.
One embodiment of the invention relates to a cardiac defibrillator for discharging an electrical charge into a patient. The cardiac defibrillator includes a device for storing mechanical energy, a generator, a capacitor, a charging circuit, a patient interface, an input device, and a control unit. The generator, coupled to the mechanical energy storage device, converts mechanical energy stored in the mechanical energy storage device into electrical energy. The charging circuit, coupled to the generator and the capacitor, transfers the electrical energy to the capacitor, wherein the electrical energy is stored in the capacitor. The patient interface, coupled to the capacitor and the patient, provides an electrical path for discharging the electrical energy stored in the capacitor into the patient. The input device generates a discharge signal. The control unit, coupled to the capacitor and input device, controls the discharge of the electrical energy into the patient in response to the discharge signal.
Another embodiment of the invention relates to a medical device configured to interface with a patient. The medical device comprises a device for storing mechanical energy and a generator. The generator, coupled to the mechanical energy storage device, converts mechanical energy stored in the mechanical energy storage device into electrical energy used to power the medical device.
Another embodiment of the invention relates to a method for powering a medical device by imparting potential mechanical energy into a mechanical energy storage device, converting the potential mechanical energy of the mechanical storage device into electrical energy with a generator, and powering the medical device using the electrical energy.
Another embodiment of the invention relates to a medical device including means for storing mechanical energy, means for converting the stored mechanical energy to electrical energy and control means coupled to the converting means for controlling the medical device.
Other principle features and advantages of the present invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description, and the appended claims.